1. Field of the Invention
The invention relates to an electronic apparatus that has a plurality of keys arranged thereon, and that can prevent an undesired operation from occurring due to a specific key being accidentally pressed.
2. Description of the Related Art
Electronic apparatuses exist that have a plurality of keys arranged on a front of their housing. For example, word processors, cellular phones, mobile computers, PDAs (Personal Digital Assistants), tape writers, have such an arrangement and can print desired characters and symbols on a printing medium, such as on a length of tape, etc.
The tape writer is described as an example of such a device. The tape writer is provided with a liquid crystal display for displaying the contents to be printed, and a plurality of keys, such as a power key for turning power of tape writer on/off, character input keys for inputting desired characters by an user, a tape feed key, a tape take-up key, and a print key for starting printing on tape.
When printing is performed on the tape using such a tape writer, the user turns the power of the tape writer on by pressing the power key. After that, the user inputs desired characters and the like by pressing the character input keys and then pressing the print key after confirming that the desired characters are displayed on the liquid crystal display. By doing so, the desired characters are printed on the tape. The printed tape is automatically cut by a cutter or cut by a cutting operation by the user.
A handheld tape writer that has a relatively small housing is an example of such a tape writer. The user can easily carry the handheld tape writer, and can obtain a printed tape on which desired characters are printed by performing a key operation while holding the housing of the handheld tape writer with one hand.
However, a situation in which the user accidentally presses an undesired key often occurs in such a handheld tape writer. This occurs because the user presses the key with one hand while holing the housing with another hand, or the user presses the key with his/her thumbs while holding the housing with both hands, which occurs since the housing is small. For example, when the print key is pressed by accident, the tape printing is started even though desired characters are not completely input. As a result, the tape is wasted. When the power key is pressed by accident while characters are being input, trouble occurs such that input character data is lost.
In order to avoid such troubles, it is conceivable that an undesired operation due to an accidental key pressing can be prevented by changing a mechanical structure of specific keys, such as the print key and the power key, so that a key contact is not made unless a force is applied to the specific keys which is stronger than a force applied to the other keys. However, implementing this solution complicates the structure of the tape writer since the structure of a few of keys needs to be changed which increases the parts count. Further, a manufacturing process becomes complicated and manufacturing costs increase.
It is also conceivable that the undesired operation can be prevented by making the structure of a specific key such that it cannot be pressed by general operation. For example, the specific key can be enclosed with protrusions, or can be provided with a cover, or only pressing a combination of the specific key and a predetermined key (e.g., the specific key and the predetermined key are simultaneously pressed) results in the tape writer detecting that the specific key has been pressed. However, it is still necessary to change the structure of the housing where the specific key is arranged. Accordingly, the structure of the tape writer becomes complicated and the parts count increases. Further, the manufacturing process becomes complicated and manufacturing costs increase. Furthermore, this structure is subject to the disadvantage that it is difficult for users to press the specific key.
The invention provides an electronic apparatus having a plurality of keys arranged thereon, wherein an undesired operation is prevented from occurring when a specific key is pressed by accident, and the specific key can be pressed by an user without any troublesome operation. This advantage is achieved without changing the mechanical structure of the specific key.
According to the invention, an undesired operation can be prevented from occurring without changing a mechanical structure of a specific key by which a function that occurs the critical incorrect operations when a key is pressed by accident is set to a first key.
In order to achieve the above object, an electronic apparatus is provided that has a plurality of keys, including a first key and a second key arranged on the electronic apparatus. In the electronic apparatus, a first key minimum pressing time that is required to detect that the first key has been pressed is longer than a second key minimum pressing time that is required to detect that the second key has been pressed. According the structure described above, the length of the first key minimum pressing time is longer than the length of the second key minimum pressing time. Therefore, the pressing of the first key is detected when the first key is pressed for a longer amount of time than the second key. Accordingly, critical incorrect operations can be prevented without changing the mechanical structure of the key by which the function that occurs the critical incorrect operations when the key is pressed by accident is set to the first key.
Further, an electronic apparatus may include a plurality of keys, including a first key and a second key that are arranged in a matrix, and a key scan detector that detects a key has been pressed by scanning the plurality of keys one after another at predetermined scan intervals. In the electronic apparatus, the key scan detector detects that the first key has been pressed if the first key is continuously in a pressed state for at least a first predetermined number of scans. The key scan detector detects that the second key has been pressed if the second key is continuously in the pressed state for at least a second predetermined number of scans which is less than the first predetermined number of scans. According to the structure described above, the first predetermined number of scans is larger in number than the second predetermined number of scans, so that the first key is not detected as having been pressed unless the first key is pressed for a longer amount of time than the second key. Therefore, the critical incorrect operations can be prevented from occurring in the electronic apparatus without changing the mechanical structure of the key by which the function that occurs the critical incorrect operations when the key is pressed by accident is set to the first key.